Galatians 4:28-31

Now we, brethren, as Isaac was, are children of promise. But, as he who was born according to the flesh then persecuted him who was born according to the Spirit, even so it is now. Nevertheless what does the Scripture say? “Cast out the bondwoman and her son, for the son of the bondwoman shall not be heir with the son of the freewoman.” So then, brethren, we are not children of the bondwoman but of the free.